The present invention relates to an apparatus for switching off and deviating a circulating liquid flow without water hammering.
This apparatus has been specifically designed to be used in a valve assembly applied in drilling systems, for preventing the liquid flow from being shut off as the drilling rods are changed.
As is known, drilling systems conventionally use drilling rods, or pipes, into which a drilling fluid (or drilling mud) is pumped so designed as to hold controlled ground hydrostatic properties, to allow drilled waste materials to exit soil, and moreover to properly lubricate and reduce the temperature of the drilling implement, thereby extending the useful life and efficiency of the latter.
The mud hydraulic circuit is a closed system and constists of a tank, one or more pumps, a duct and valve system (probe manifold) to direct the liquid flow through the well being drilled.
More specifically, the drilling mud passes through a driving head and is conveyed into the drilling rods up to the drilling implement or bit, from which it is ejected to perform the above mentioned operations.
Then, the ejected mud is caused to move upward through the well, in the gap between the drilling rods and the borehole up to the well surface where it is conveyed through further ducts and valves to further devices operating for filtering and reconditioning the used drilling mud, to be then sent to the mud tank in order to be pumped again through the well circuit.
As a new drilling rod is applied to or removed from the drilling string, it is necessary to shut off the fluid circulation.
This operation is a rather dangerous one since, during the switching off of the mud pumps and upon stopping the mud flow conveyed through the well, inside the drilled borehole a pressure compensating cycle operation occurs, due to the change of the pressure load or stress arrangements from a dynamic to a static liquid condition, which could cause a lot of drawbacks, among which an accidental and uncontrolled soil fracturing.